1. Field of Invention
The present invention relates to a telephone network and a method of call processing in a telephone network.
In the present application, “enhanced service” means any service provided to a subscriber other than simple connection made, in response to dialling by a caller, between the terminal equipment from which the caller attempts to establish the call and another, “target”, terminal equipment to which the attempt is made, and the associated signalling of ringing, engaged status and number unobtainable. The enhanced service may be provided to either the subscriber making the call attempt (for example call barring) or to the subscriber at the target terminal equipment (for example voice mail).
2. Description of Related Art
It is known to provide such enhanced services, sometimes known as “intelligent network” services, in telephone networks. The processing required to implement such services can be carried out by a telephone switching centre. However, this has been found to be undesirable because telephone switching equipment manufacturers must customise their switches according to different network operators' requirements. This increases the cost of such equipment.
An alternative approach is to use a relatively simple switching centre in conjunction with an enhanced service processing apparatus, or “service control point”. In this arrangement, the switching centre notifies the enhanced service processing apparatus of an attempt to establish a call connection and the enhanced service processing apparatus returns switching control commands such as “proceed as normal” or “bar call”.
A third approach, exemplified in International Patent Specifications WO97/48238 and WO96/13949 also use an enhanced service processing apparatus, but this is invoked only if the switching centre identifies the call as being of a type which may require enhanced processing, either because the digits dialled identify a target party for which enhanced processing capability is required, or because such capability has been previously specified for the calling party.
A disadvantage with these approaches is that there is often a lot of traffic between the switching centres and the enhanced service processing apparatus consisting of notifications of call connection establishment attempts and “proceed as normal” commands, for example, if the conditions for call forwarding are not met (line not busy, wrong time of day, etc). This extra traffic, and the extra processing carried out by the enhanced service processing apparatus, can impede the efficient operation of the enhanced services processes. It is an aim of the present invention to solve or ameliorate the aforementioned problem.